Laminated article



. lubricant plasticizer.

Patented Nov. 15. 1938 LAMINATED ARTICLE John W. Haught, Arlington, N. .L, assignor, by, mesne assignments, to E. I. du Pont de N emours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application February 13, 1936,

' .Serial No. 63,732

3 Claims. '(01. 49-81) ventional plasticizers it;has not been possible,

heretofore, to obtain satisfactory interlayer sheeting of a cellulose nitrate plastic which, when used as an interlayer in safety glass, does not either develcp'bubbles on short exposure to sunlight or become brittle when subjected to winter temperatures.

An object of the present invention is to provide, for use in safety glass and other laminated articles, cellulose nitrate plastic interlayer sheeting which possesses good strength and toughness and retains this desirable strength and toughness over the range of temperatures of use of safety glass. A further objectis to provide an interlayer which, when used in safety glass, does not develop bubbles under ordinarily severe conditions of service and is; not susceptible to appreciable discoloration by sunlight.

The above objects are-accomplished according to the present invention by the use in laminated articles generally, and safety glass specifically, of

,interlayers comprising 100 parts, by weight, of

cellulose nitrate and -150 parts, by weight, of a plasticizer composition therefor comprising 83- 17% of an active plasticizerand 17-83% of a lubricant plastlcizer. Preferably, the interlayer sheets comprise parts, by weight, of cellulose nitrate and 80-115 parts, by ,weight, of a plasticizer composition therefor comprising 72- 50% of an active plasticizer and 28-50% of a All parts and percentages throughout the specification and claims are given by weight and not by volume.

The term active plasticizer, as used herein,

denotes ,a group of compounds which do not.

colloid anhydrous cellulose nitrate at room temperature but do colloid anhydrous cellulose nitrate at C. and which have boiling points substantially above 300 C. at atmospheric pressure. This group of active plasticizers, of which one or more may be utilized in the present invention, includes the following:

Di-alkyl phthalates in which the alkyl groups contain from 4 to 8 carbon atoms, inclusive. Di-meth'ylcyclohexyl adipate,

Di-amyl succinate,-

Di-methylcyclohexyl oxalate,

Butyl phthalyl butyl glycollate. I

: The term "lubricant plasticizer, used herein,

temperature or at 120 C. but have at least a swelling action upon anhydrous cellulose nitrate at 75 C. when in admixture with from 15-40% of their weight of ethyl alcohol. These compounds include the group of alkyl esters of saturated aliphatic acids in which either the alcoholic or acidic constituent is a saturated aliphatic radical having 818 carbon atoms, inclusive, and the other constituent is a saturated aliphatic radical having less than 8 carbon atoms, the ester having a total of 14 26 carbon atoms, inelusive, and the group of phthalic acid esters in which the esterifying group is'a saturated aliphatic radical having 10-14' carbon atoms, inclusive. 1

If the lubricant plasticizers are used as sole plasticizers for the cellulose nitrate, the resulting interlayer sheets are of good toughness and pliability but incapable of being satisfactorily bonded to glass.

Among the lubricant plasticizers particularly suitable for use in the present invention are the following:

Ethyl palmitate,

Methyl palmitate,

Ethyl laurate,

Methyl esters of hydrogenated cocoanut oil acids,

It has been discovered that, if an active plasticizer is used with one of these lubricant plasticizers, the cellulose nitrate interlayer sheeting plasticized with the mixture possesses remarkable and unexpected properties which make it uniquely valuable for use in safety glass, and the like. Such sheeting is characterized by unusual'insensitivity. to water, great toughness at winter temperatures, and, at the same time, exhibits quite unexpected retention of strength and toughness at temperatures up to 50 C., a desirable degree of pliability with little or no sacrifice of strength as compared to the conventional cellulose ester interlayer sheets, great tearing strength, a high degree of resistance to bubbling on exposure to sunlight, and a high degree of resistance to discoloration.

The proportions of active and lubricant plasticizers may be varied according to the relative strengths of their colloiding actions and, particularly, according to the strength of solvent action of the lubrication plasticizer. With a lubricant plasticizer which has very weak solvent action, it is advantageous to employ a larger proportion of active plasticizer than with a lubricant plasticizer which possesses greater colloiding effect.

The plasticizer composition for the cellulose nitrate, according to the present invention, may be varied from 83-17% of active plasticizer and 17-83% of lubricant plasticizer but it is preferred to keep within the proportion of '72 to "50% of the active plasticizer and 28 to 50% of the lubricant plasticizer.

In general, the proportions of lubricant plasticlzer to active plasticizer will be less the greater the total amount of plasticizer as the amount of lubricant plasticizer should be held suiiiciently low to avoid formation of interlayer sheeting which cannot be satisfactorily bonded to glass.

While definite proportion ranges have been given above in order to more clearly teach the art the present invention, it will be understood that the optimum specific proportion of a particular lubricant plasticizer with a particular active plasticizer will be established within the range of proportions given, by those skilled in the art, by keeping in mind the general considerations disclosed above in arriving at a satisfactory ratio of the two types of plasticizer.

The following examples are given to illustrate specific embodiments of the present invention:

Example 1 Parts Cellulose nitrate Diamyl phthalate 80 Octadecanediol-LIZ diacetate 34 Denatured alcohol 40 The ingredients are colloided in a Werner and Pfleiderer mixer, filtered by hydraulic pressure through heavy muslin, rolled to remove excess solvent, consolidated by heat and pressure, and from the resulting block sheets of approximately 0.025 inch caliper are sliced. These sheets are seasoned, i. e., treated to remove substantially all of the volatiles but no substantial part of the plasticizer. Sheets are laminated between glass plates, using as adhesive a solution of 1 part cellulose nitrate and 3 parts diamyl phthalate in suitable volatile solvents, and subjecting to a' temperature of about C. and a pressure of 150 lbs. per square inch.

These laminations have good resistance to sudden impact at both ordinary and low temperatures and will bubble and discolor only after prolonged exposure to sunlight or uviarc light, (more than 200 hours in the standard test in which a specimen of interlayer composited between glasses is exposed under definite conditions to the light of a quartz-tube mercury-vapor lamp operated at :5 volts and consuming 900 watts). The samples are at a distance of 9 inches from the tube; This test is in the nature of an accelerated test, as the changes taking place occur very much more quickly than they would in sunlight.

In the following examples merely the composition of the interlayer sheet is given since the procedure was substantially identical with that set forth in Example 1:

Example 2 Parts Cellulose nitrate 100 Diamyl phthalate 50 Ethyl laurate 35 Denatured alcohol 40.

Example 3 Parts Cellulose nitrate 100 Mixture of isomeric hexyl, heptyl and octyl phthalates Didecyl succinate 34 Denatured alcohol 40 Example 4 Parts Cellulose nitrate 100 Phthalic acid esters of mixture of isomeric alcohols, principally of 6, 7 and 8 carbon atoms, formed as by-products in synthesis of methanol 100 Octadecanediol-l,12 diacetate 40 Denatured alcohol 40 Example 5 Parts Cellulose nitrate 100 Diamyl succinate 49- Octadecanediol-1,12 diacetate 34 Denatured alcohol 40 Example 6 Parts Cellulose nitrate 100 Di-methylcyclohexyl adipate 49 Octadecanediol-1,12 diacetate 34 Denatured alcohol 30 Example 7 An interlayer sheeting composition comprising:--

Parts Cellulose nitrate 100 Diamyl phthalate 63.5

Phthalic esters of mixed saturated fatty alcohols derived from acids of cocoanut oil by hydrogenation 34 Denatured alcohol 75 C. P. acetone; 25

was colloided and filtered and the resulting colloid extruded by suitable means in the form of a wide ribbon through an orifice. The balance of the treatment is as in Example 1.

The following examples illustrate suitable interlayer sheeting compositions adapted to be worked up in accordance with the procedure in Example 7:

Example 10 Parts Cellulose nitrate 100 Diamyl phthalate 80.5 Ethyl palmitate 25 Denatured alcohol C. P. acetone 25 Example 11 Parts Cellulose nitrate 100 Phthalic acid esters of mixture of isomeric alcohols, principally of 6, 7 and '8 carbon atoms, formed as by-products in synthesis of methanol 34 Dibutyl phthalate 15 Octadecanediol-1,12 diacetate 34 Denatured alcohol 75 C. P. acetone 25 Example 12 Parts Cellulose nitrate 100 Diamyl phthalate 80.5

Phthalic esters of mixed saturated fatty alcohols derived from acids of cocoanut oil by hydrogenation 34 Denatured alcohols 75 C. P. acetone 25 It will be understood that the above examples are merely illustrative and that the invention broadly comprises the use of interlayer compositions as set forth hereinbefore.

In the specific examples no mention is made of stabilizers or of coloring ingredients but it will be understood that these will be used if and when required, in accordance with established practice in the art. Also, it should be noted that the plasticizer proportions are given in connection with the amount of plasticizer initially introduced in making up the plastic. However, all of the plasticizers herein considered are so highly non-volatile that no appreciable loss results in the manufacture of the interlayer sheeting and hence substantially the same proportions of plasticizer are found in the finished interlayer sheet as were used in making up the plastic composition.

The present invention is not concerned with the method of preparation of the sheeting, which may be accomplished by any of the known methods adapted to give a sheeting meeting the ordinary strict standards of the art as regards cleanness, clearness, correctness of color, uniformity of thickness, and the like. The invention is also independent of the manner in which the interlayer sheet is combined with the glass sheets to form the laminated glass. Interlayer sheets made according to the present invention may be satisfactorily laminated with glass by any of the standard methods already established, either with or without adhesives.

While the invention primarily relates to laminated glass, it will be understood that the interlayer sheets of the present invention are likewise well adapted for the lamination of brittle sheets generally. The laminated articles according to the present invention may consist of a single sheet of glass, or other brittle material, with a single sheet or layer of plastic bonded thereto. or they may comprise a plurality of sheets of glass with interposed plastic interlayers.

The invention permits advantage to be taken of the recognized merits of cellulose nitrate as the base material for interlayers for laminated glass, while at the same time eliminating the defects which have heretofore characterized such interlayers.

Interlayer sheeting made in accordance-with the present invention possesses a high degree of insensitivity to moisture, which promotes the permanence of the bond between the interlayer and the glass and which suppresses any tendency of the cellulose nitrate to suffer hydrolysis during the service of the laminated glass. The interlayer possesses great toughness and consequently produces a laminated glass of excellent protective qualities. Furthermore it retains this toughness both at winter temperatures and at summer temperatures. With the toughness which makes for strong protective characteristics, is coupled a desirable degree of pliability, permitting broken composite pane to yield under impact and thus reducing the danger of personal injury by concussion.

As a means of determining the degree of impairment of the protective character of the laminated glass by winter temperatures, it is customary to subject specimen panes to a cold break test, in which laminated glass panes nine inches square are supported around their edges upon a square frame and subjected to the impact of the fall of a two pound steel ball from a height of three feet. The test is carried out at 0 C. or -10 C.

In this cold break test" composite panes containing sheeting made in accordance with the present invention surfer merely a cracking of the glass radially from the point of impact; the pane asa whole holds together and there is no flying of fragments of glass. In short, the panes behave at the low temperatures substantially as they do at normal temperatures.

Interlayer sheeting made in accordance with the invention also passes satisfactorily the accepted test for development of bubbles under artificial ultra-violet radiation, and in actual service fails to develop bubbles under prolonged severe conditions of use.

As many apparently widely vdilferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

I claim: 1. Laminated glass comprising a sheet of glass and bonded thereto an interlayer sheet comprising 100 parts of cellulose nitrate and 60-150 parts of a plasticizer composition therefor composed of 83-17% of diamyl phthalate and 17-83% of' octadecanediol-LIZ diacetate.

2. Laminated glass comprising a sheet of glass and bonded thereto an interlayer sheet comprising approximately 100 parts of cellulose nitrate, 50 parts of diamyl phthalate, and 35 parts of cotadeca-nediol-1,12 diacetate.

3. Laminated glass comprising a sheet of glass and bonded thereto an interlayer sheet comprising 100 parts of cellulose nitrate and -115 parts of a plasticizer composition therefor composed of 72-50% of diamyl phthalate and 28-50% of octadecanediol-1,12 diacetate.

JOHN w. moan'r. 

